Metal fabrication



Nov. 2, 1965 T. F. PAULS METAL FABRICATION 3 Sheets-Sheet 1 OriginalFiled Aug. 29, 1962 WWIHHIHHHHIIW INVENTOR. THE/FUN F PAULS Y B WATTORNEY Nov. 2, 1965 T. F. PAULS METAL FABRICATION Original Filed Aug.29, 1962 3 Sheets-Sheet 2 III- 1 FIG 9 INVENTOR Thf/PON PAULS ATTORNEYNov. 2, 1965 T. F. PAULS 3,215,196

METAL FABRICATION Original Filed Aug. 29, 1962 3 Sheets-Sheet 3 FIG- 10FIG J1 I: INVENTOR. w THE/P01! F PAULS ,I V) r I v A TI'ORNEV UnitedStates Patent 3,215,196 METAL FABRICATION Theron F. Pauls, Alton, Ill.,assignor to Olin Mathieson Chemical Corporation, a corporation ofVirginia Original application Aug. 29, 1962, Ser. No. 220,195, nowPatent No. 3,172,194, dated Mar. 9, 1965. Divided and this applicationJune 24, 1964, Ser. No. 384,016

2 Claims. (Cl. 165-179) This application is a division of co-pendingapplication Serial No. 220,195 filed August 29, 1962, now Patent No.3,172,194 granted March 9, 1965, which was a continuation-in-part ofco-pending application Serial No. 556,225 filed December 29, 1955.

This invention relates to a heat transfer device and more particularlyto a heat exchanger tube having integral fins.

It is desirable that heat exchange tubing for boilers, refrigerators,condensers and the like he provided with external fins. Such heattransfer fins are usually brazed or soldered on the tubing except wherethe tube structure is very heavy and permits the fins to be cast,extruded, or rolled. However, especially where the tubing is of the flator oblong sheet metal type, thin walled tubing and the fins are usuallybrazed or soldered together. This is not only expensive and timeconsuming, but frequently fails to result in a rigid and etficientjoint. Generally, a brazed or soldered joint is of reduced heat exchangeefliciency for lack of unimpeded heat transfer through the joint.Another heretofore known method of forming fins is a helical rollingmethod which, however, has the disadvantage of requiring a fully formedround tube blank together with an internal mandrel and which has thefurther disadvantage of requiring a considerably thick tube wall andcomplicated apparatus and controls for the proper extension of integralfins. This prior method is not readily adapted to formation of fins inconjunction with relatively thin sheet metal walls.

One object of this invention is to provide a simple lowcost but improveddesign of finned heat exchanger tube. Another object is to provide athin-walled, relatively flat, sheet metal tube having a plurality ofintegral fins on the external and internal surfaces of the tube forimproved heat transfer efliciency. Another object is to provide animproved method for making a tubular form of heat exchanger unit havingextended heat transfer surfaces and of improved heat transferefficiency. A further object is to provide a method adapted to highspeed mass production of finned tubing from sheet metal.

Other objects and advantages will become more apparent from thefollowing description and drawings in which:

FIGURE 1 is a plan elevational view of a typical portion of oneembodiment of this invention;

FIGURE 2 is a cross-sectional view taken along lines IIII of FIGURE 1;

FIGURE 3 is a perspective view of the embodiment of FIGURE 1 withportions broken away and shown in section on lines III-III of FIGURE 1;

FIGURE 4 is a cross-sectional view taken along lines IV-IV of FIGURE 2;

FIGURE 5 is a fragmentary view in cross-section showing a flatuninflated tube sheet between grooved die platens suitable formanufacturing the embodiment of FIGURES 1 to 4;

FIGURE 6 is a fragmentary cross-sectional view taken along lines VIVI ofFIGURE 5;

FIGURE 7 is a fragmentary cross-sectional view illustrating a furtherstage in the use of the device shown in FIGURES 5 and 6;

FIGURE 8 is a cross-sectional view of another embodiment of thisinvention shown in conjunction with the apparatus used in itsmanufacture;

and

FIGURE 12 is a semi-diagrammatic representation of portions of swagingrolls capable of forming the fin structure shown in the embodiments ofFIGURES 10 and 11.

In the aforesaid co-pending application, Serial No. 556,225, there isshown a novel method of fabricating a new type of finned tubingcharacterized by a relatively thin-walled structure compared to theextension of the formed fins. This type of structure is particularlyadaptable to the manufacture of integrally finned tubing from a flat,collapsed but inflatable tube blank. The invention in this co-pendingapplication contemplates the provision on the external surface of anelongated tubular walled sheet metal blank of transversely andlongitudinally extending fins together with thin intervening wallportions. In accordance with the invention of this co-pendingapplication an elongated tube blank is provided having double walls theopposed interior surfaces of which are contiguous but separable formingpredetermined areas therebetween corresponding to a desired passagewaysystem. These types of structures are exemplified by those obtained inaccordance with the well-known method of -U. S. Patent No. 2,690,002,granted September 28, 1954, to L. H. Grenell. In one embodiment of thisinvention the walls of this type of structure are formed by pressurewelding component sheets together in preselected areas between themwhile simultaneously forging opposed tube walls to swage fins from thematerial of the walls. Adherence is prevented by coating thesepreselected areas with stop-weld material which separates the componentsheets during the deformation operation While the fins are being forgedor swaged from the sheet material of the walls which are preferably ofsheet metal.

In a preferred embodiment of the invention of this copendingapplication, the fins are preferably formed in a direction transversethe elongation of the sheet unit.

In accordance with this invention, it has been discovered that a finnedtubing of greater efficiency and extended surface can be obtained byforging the tube blank to upset or swage fins thereon with the fins onone of the external surfaces, of the blank, being in alternate offsetrelationship with the fins formed on the other external surface of thetube blank. In addition, the forging is done under sufficient pressureto induce internal metal flow within the tube blank which deforms orcorrugates the interface between component sheets to form projections onthe adjacent internal face between the component sheets disposed inintermeshed relationship with each other. The foregoing is accomplishedby a device having opposed teeth or pressure points with the pressurepoints of one side being staggered with respect to the pressure pointson the other side. Upon distention and separation of the intermeshedinternal projections the spaced-apart tube Walls are provided withinwardly extending fin projections which additionally increase the heattransfer area of the tube blank and further provide means for inducingturbulence in the fluid flowing within the tubular structure.

More specifically with reference to the drawings, a specificillustrative embodiment of this invention is shown in FIGURES 1, 2, 3and 4 which consists of a first said wall 1, the opposite side wall 2both of which are integrated or preferably joined together by pressurewelding at the lateral edges 3 and 4 so as to form at these lateraledges a unitary structure completely sealed together and requiring noextraneous brazing or welding materials. Side wall 1 bears a series ofexternal fins 5, while side wall 2 bears a second series of externalfins 6. The fins are integral with the tube walls, however, each of thefins 5 in the first series is in offset relationship with correspondingfins 6 of the second series. In addition, side wall 1 is also providedwith a series of internal fins 7 projecting inwardly within the tubestructure. Also the side wall 2 bears a similar series of fins 3projecting inwardly of the tube structure in opposed direction to thefins 7 on side wall 1. In the specific embodiment illustrated, fins 7and 8 form in effect transverse crimps or ruffies functioning astransverse fin projections with the fin projections 7 of side wall 1being in offset relationship with corresponding fin projections 8 ofside wall 2, with each series of fin projections forming acorrugated-like surface on the corresponding finned walls carrying them.Further, the internal fin projections 7 on side wall 1 are also inoffset relationship with the external fin projections 5 on this sidewall. In like manner, the internal fin projections 8 on side wall 2 arein offset relationship with the external fin projections 6 on this sidewall.

As will be appreciated this construction greatly extends the heattransfer area of the tubular srtucture to provide improved heatexchange. The single fluid passageway 9 may be generated by bulging ofthe finned walls 1 and 2 in any suitable manner but preferably byinflation, and, as also illustrated, is of lenticular shape. As will beobvious the shape of this passageway can be of various configurationsfrom extremes of an ovoid shape to a rather fiat oblong or nearlyrectangular shape.

The fins of the embodiment of FIGURES 1 to 4 can be formed withapparatus such as illustrated in FIGURES 5 to 7 where 19 is a workingend of an upper forging die and 11 is the working end of a lower forgingdie adapted for reciprocating cooperating relationship by means Wellknown in the art. These forging dies are i1- lustrated as operating on aspecial flat laminated stock generally indicated at 12 having opposedcomponent layers 13 and 14 joined at their lateral edges 15 and 16 butmaintained in separation at 17 in any suitable manner while incontiguity. For example, at 17 there may be provided a thin layer of anysuitable Weld or adherence preventing material.

Die block 10 is provided with a series of grooves between protrudinglands 18. In similar manner, die block 11 has a grooved working faceprovided with a series of spaced lands 19 for cooperating coaction withlands 18 of die block 10. However, the lands 18 of die block 10 are inoffset relationship with lands 19 of die block 11 as a result of which,during forging, the opposed series of lands exert coextending areas ofpressure to upset and deform the surface of the metal into external finprojections and concurrently induce suflicient flow of metal within thelaminated stock 16 to deform the interface or line of separation 12between component layers 13 and 14 to form the desired internal finprojections on the adjacent face of the component layers. As a result ofthis forging operation the laminated stock is swaged to produce theexternal fin projections 5 and 6 disposed in offset relationship to eachother and the internal fin projections 7 and 8 in offset and intermeshedrelationship With one another with their interface defined by thecorrugated line of separation 20.

In addition, in the specific embodiment shown, each of lands or teeth 18and 19 are shaped by lengthwise tapering to be of greatest protrusionwhich is to say greatest approach, adjacent their mid-section withrespect to the corresponding opposing lands. Such a die face arrangementworks the greatest deformation of component sheets 13 and 14 adjacentthe longitudinal mid-plane structure 12 to provide there the greatestextension of the fins 5 and 6. Upon engagement of forging dies 10 and 11into the laminated stock or blank 12 with the desired pressure orimpact, the result nt uneven deformation of the blank also shapes theintegral fins 5 and 6 to be tapered down in the ends 21, 22, 23, and 24as shown in FIGURES 1 to 4. The resultant blank, now not only internallylaminated but also externally and internally finned, may be, with orwithout annealing, suitably distended or bulged by injection of aninflation fluid pressure along the interface or unwelded area 20 anderection of the side walls 1 and 2 and generation of the internalpassageway 9. It is noted that the forged blank may be distended byinfiation either freely or between sizing dies to give a desiredlongitudinal uniformity during the distention.

The embodiment of the tube structure of this invention, shown in FIGURE8, is characterized by a streamline or tear drop cross-sectionalconfiguration. In this embodiment, the finished tube consists of sidewall 25 which bears a series of external fins 26 in offset relationshipto a similar series of external fin projections 27 extending from theopposite side wall 28. These external fin projections of this embodimentare of greatest outward extension adjacent the leading lateral edge 29which in conjunction with the leading edge 30* of external fins 25 andthe leading edge 31 forms a generally rounded streamline leading finsection. Adjacent the trailing lateral edge 32 of the tube, the fins 25and 28 are tapered down to merge gradually into the opposing side walls25 and 28, which as in the previous embodiment are integrated at bothlateral edges 29 and 32. In addition, this embodiment is also formedwith internal fin projections 33 extending internally from the innersurface of said wall 25 with internal side projections 34 extendinginternally from inner surface of side wall 28 with each of the internalfin projections 33 being in offset relationship with corresponding finprojections 34 of side wall 28. In addition, the internal finprojections 33 on side wall 25 are in offset relationship with theexternal fin projections 26 on this wall.

This embodiment of FIGURE 8 can advantageously be formed from aninternally laminated blank 35 in the apparatus shown in FIGURE 9, afterthe structure is infiated to the final finished form shown in FIGURE 8between the spaced sizing platens 36 and 37, the working faces of whichare closely spaced adjacent the trailing end 32 and more remotely spacedadjacent the leading edge 29. In the fabrication of this embodiment, theinternally laminated blank 35, preferably in completely annealedcondition, is placed in the die cavity of the block 38 (FIG- URE 9)where it is supported on the grooved working face of the lower movableforging ram 39, also nested in the cavity of the block 38. Upper forgingram or die 40 is movable into the cavity of block 38 and is adapted,together with the lower ram 39, to subject the laminated blank 35 to aforging or swaging action. As will be noted, in the apparatus of FIGURE9, the lateral edges of the blank are confined, thus edge 41, which Willform trailing edge 32 of the finished tube, and also edge 42 of blank39, which will form the leading edge 29 of the finished tube, areconfined in the cavity of die block 38. Working faces of the forgingrams 39 and 40 are provided with a series of spaced teeth or lands 43and 44, respectively, with the lands 43 in one series being in offsetrelationship with the lands 44 of the other series in a manner similarto that of the preceding embodiment. As will be noted, forging lands 43and 44 are tapered back as to approach edge 41, of the laminated blank35, and to accomplish less finning and forging of the laminated blank35. Although specific configuration of forging lands has been shown, itis to be understood that the forging lands 43 and 44 may extenduniformly all the Way across the working face of the forging rams 39 and40, respectively, to provide fins substantially completely across thetube structure, as, for example, shown in FIG- URES 10 and 11.

Upon completion of the forging operation the swaged blank 35, nowprovided with a series of internal and external fins on both sides ofcomponent sheets 45 and 46,

is then placed between suitably separated platens 36 and 37 (FIGURE 8)and subjected to internal inflation pressure so as to produce the spaceof the finished tube shown in FIGURE 8 having fluid passageway 47.

In any event, by the production of the foregoing and other embodiments,there is provided a flat, two-walled blank in any suitable manner. Suchblank may be formed by rolling or drawing a relatively thin-walled tubeshut. Also the blank may be formed by extrusion after which the extrudedblank may be flattened either by rolling or passage through a sizing ordrawing die. If naturally occuring oxide within the interior of such ablank is insuflicient for purposes of preventing welding, a coating ofstop-weld material may be applied to the interior of the blank so as toprevent the undesired welding or sticking between the opposing innerwalls of the blank during the rolling, drawing, or subsequent forgingoperation described herein. However, as indicated above a preferred modeof providing the blank is by the method described in the aforesaid U.S.Letters Patent No. 2,690,002 which method comprises superimposing twometal sheets together having between them an intervening layer ofstop-Weld material extending in a pattern corresponding to a desiredfluid passageway system, followed by presusre welding the sheetstogether in their adjacent areas not separated by the stop-Weld materialin any appropriate manner. This type of blank is then suitable and readyfor forging or swaging thereof to form the desired finned structure.

FIGURE illustrates another embodiment of this invention wherein a straptype of heat exchanger 50 is made in accordance with this invention. Theunit is provided with a single heat exchanger fluid passageway 51, oneend of which at 52 is constricted so as to enable an inlet connection tobe made with ordinary tubing 53. In the other end 54, the unit issimilarly constructed for connection with outlet tube 55. Between theseends there is provided on the exterior surface of the unit 50 a seriesof transverse integral fin structures such as 56 extending all the wayacross the unit 50 including lateral edges 57 and 58. As with thepreceding embodiments, the fin structures projecting from one externalsurface of the unit 50 are in offset relationship with the finsprojecting from the opposite surface of this unit. Also, in accordancewith this invention, the unit is provided with internal fins on each ofthe inner surfaces of tube walls 59 and 60, as for example, the finprojection 61 on the inner surface of tube side wall 60. In mannersimilar to that of the preceding embodiments, the internal finprojections, such as 61, are in offset relationship to the external finprojections provided on the common tube side wall.

To produce the external and internal fins of the foregoing embodiment,they may be formed by means of swaging rolls 62 and 63 of FIGURE 12instead of the reciprocating forging dies described hereinbefore. Rolls62 and 63, the latter of which may be flanged on both the ends have aperipheral construction suitable for manufacturing the fin structure andstrip of FIGURE 10. It is to be understood that the roll periphery maybe of grooved or toothed form identical or similar to the workingfabrication shown in FIGURES 5 and 9. Each roll is provided withprotruding forging teeth or lands such as 64 of roll 62 and teeth 65 ofroll 63. These teeth are designed so that the teeth 64 of roll 62 are inoffset relationship with the teeth 65 of roll 63 at the roll bite atwhich the roll spacing is adapted to accomplish the desired swaging forflow of metal needed to make the fins. The rolls 62 and 63 may each befree over a portion of their peripheries such as shown at 66 and 67,respectively, so that these recessed portions of the periphery mayrender the ends 52 and 54 of the unit of 6 FIGURE 10 free from fins. Inthese recessed portions of the .rolls 62 and 63 there is provided a pairof registrable pinch-off sharp protrusions such as 68 and 69,respectively. When these come together in the substantial contact andregistry desired, measured portions of the strip are cut apart from eachother.

In similar manner to the foregoing embodiments, FIG- URE 11 illustratesa further modification of this invention depicting the provision of finson a tube sheet 70 containing internally therein a system ofinterconnected fluid passageways 71 comprising, as for example, fluidpassageways 72 interconnected together by a cross header 73. Thisembodiment may be provided by any of the foregoing methods with externalfin projections on each of the external surfaces of unit 70, as forexample, the fin projections 74 illustrated in FIGURE 11, with thetransversely extending fins on one external surface disposed in offsetrelationship with transverse fin projections extending on the oppositesurface of the unit 70. In addition, the unit 70 is also provided withtransverse internal fin projections 75 on the inner walls of each of thetube side walls, such as fins 75, in the offset relationship with eachother hereinbefore described.

Although the invention has been described with respect to specificembodiments and details, various modifications of this invention will beapparent to one skilled in the art and are contemplated to be embracedwithin the invention.

What is claimed is:

1. A hollow metal tube sheet structure comprising (A) a seamlessintegral sheet of metal,

(B) at least one tubular passage within said sheet defined by first andsecond longitudinally extending opposed tube side walls,

(C) a plurality of first fins on the external surface of said first sidewall disposed transverse the axis of said tube in spaced relationship,

(D) a plurality of second fins on the external surface of said secondside wall distinct from said first fins, said second fins being disposedtransverse the axis of said tube in spaced relationship, said secondfins being in offset relationship With respect to said first fins,

(E) a plurality of first projections on the inner surface of said firstside wall disposed transverse the axis of said tube and in offsetrelationship with respect to said first fins, and

(F) a plurality of second projections on the inner surface of saidsecond side wall distinct from said first projections, said secondprojections being disposed transverse the axis of said tube and inoffset relationship with respect to said second fins and with respect tosaid first projections.

2. The structure of claim 1 wherein said first projections are separatedby depressions of a configuration matching that of said secondprojections.

References Cited by the Examiner UNITED STATES PATENTS 2,017,201 10/35Bossart et al -177 X 2,179,530 ll/39' Townsend et al 29l57.3 2,463,9973/49 Rodgers 29l57.3 2,858,115 10/58 Stebbins 165179 2,960,760 11/60Woolf 29190 3,081,825 3/63 Macall 165179 3,104,161 9/63 Carlson 29190FOREIGN PATENTS 1,099,551 3/55 France.

273,721 6/ 13 Germany.

ROBERT A. OLEARY, Primary Examiner.

CHARLES SUKALO, Examiner.

1. A HOLLOW METAL TUBE SHEET STRUCTURE COMPRISING (A) A SEAMLESSINTEGRAL SHEET OF METAL, (B) AT LEAST ONE TUBULAR PASSAGE WITHIN SAIDSHEET DEFINED BY FIRST AND SECOND LONGITUDINALLY EXTENDING OPPOSED TUBESIDE WALLS, (C) A PLURALITY OF FIRST FINS ON THE EXTERNAL SURFACE OFSAID FIRST SIDE WALL DISPOSED TRANSVERSE THE AXIS OF SAID TUBE IN SPACEDRELATIONSHIP, (D) A PLURALITY OF SECOND FINS ON THE EXTERNAL SURFACE OFSAID SECOND SIDE WALL DISTINCT FROM SAID FIRST FINS, SAID SECOND FINSBEING DISPOSED TRANSVERSE THE AXIS OF SAID TUBE IN SPACED RELATIONSHIP,SAID SECOND FINS BEING IN OFFSET RELATIONSHIP WITH RESPECT TO SAID FIRSTFINS, (E) A PLURALITY OF FIRST PROJECTIONS ON THE INNER SURFACE OF SAIDFIRST SIDE WALL DISPOSED TRANSVERSE THE AXIS OF SAID TUBE AND IN OFFSETRELATIONSHIP WITH RESPECT TO SAID FIRST FINS, AND (F) A PLURALITY OFSECOND PROJECTIONS ON THE INNER SURFACE OF SAID SECOND SIDE WALLDISTINCT FROM SAID FIRST PROJECTIONS, SAID SECOND PROJECTIONS BEINGDISPOSED TRANSVERSE THE AXIS OF SAID TUBE AND IN OFFSET RELATIONSHIPWITH RESPECT TO SAID SECOND FINS AND WITH RESPECT TO SAID FIRSTPROJECTION.